Enhanced Photo-Fenton Activity Using Magnetic Cu0.5Mn0.5Fe2O4 Nanoparticles as a Recoverable Catalyst for Degrading Organic Contaminants

Abstract

Interest in using various nanoparticle catalysts to activate H2O2 with light for organic contaminant and wastewater treatment is steadily increasing. We successfully synthesized magnetically recoverable Cu0.5Mn0.5Fe2O4 nanoparticles using a simple co-precipitation method followed by melamine-assisted calcination. Material characterization revealed that melamine acted as a coordinating agent during the calcination process that promoted a ferrite structure. Copper (Cu)-substitution effectively decreased material aggregation and promoted catalytic activities. Cu0.5Mn0.5Fe2O4 nanoparticles showed outstanding catalytic performance on several organic contaminants (87.6–100.0% removal within 2 h). Using oxytetracycline (OTC) as a surrogate wastewater constituent, we found that the hydroxyl radical (•OH) and superoxide anions (•O2−) were the active radical species involved in OTC degradation. Cu0.5Mn0.5Fe2O4 nanoparticles exhibited excellent photo-Fenton catalytic ability in real wastewater and demonstrated high material stability, even after four consecutive uses (i.e., fourth cycle). In a pilot-scale experiment (10 L), we provide proof that our rigorous treatment system was able to remove remnant OTC, TOC, and also any available colloidal particles to only 1 NTU. Ecotoxicity studies using an aquatic plant (Hydrilla verticillata) and zooplankton revealed that treated water could be reused in various ratios. Furthermore, at 5% of treated water, rapid leaf recovery and a significant increase in rotifer numbers were reported. These observations support the use of Cu0.5Mn0.5Fe2O4/H2O2/light as an efficient and environmentally friendly catalytic system for treatment of organic contaminants, and a radical generating mechanism is proposed.